Fix dates in xpdom1, ordtypelem8, and phtpyhtpy
Fix dates in xpdom1, ordtypelem8, and phtpyhtpy

Fix the dates in the assertions xpdom1, ordtypelem8,
and phtpyhtpy.

Signed-off-by: David A. Wheeler <9ae72d22d8b894b865a7a496af4fab6320e6abb2@dwheeler.com>

metamath/set.mm,metamath/set.mm,metamath/set.mm